Abstract: Objective: To imporove the diagnostic level of lung adenoeareinoma in situ (AIS) by analyzing the high- resolution CT (HRCT) performance of lung adenoeareinoma in situ (AIS). Materials and Methods: The HRCT findings of 48 AIS patients were collected from 45 patients who were confirmed by operation and pathology. HRCT features as location, number, margi, size, density, lobulation sign, spiculation, vocule sign, bronchiolectasis sign, pleural indentation and the distance from the adjacent pleura were respectively analyzed. Results: Of the 45 cases (total of 48 lesions), 14 lesions were located in the upper right lung, 16 in the right upper lung, 7 in the lower left lung, 4 in the right middle lung, 7 in the lower right lung. 32 patients showed single lesion, 3 patients showed two lesions, 10 were complicated with AAH and/or MIA. The maximal diameter were 4~19.2 mm, of which 41 lesions maximal diameter less than 10mm. All lesions were pure ground glass density nodules (pGGN). The average CT value of all lesion was (-611 ±82.76) HU. 39 lesions had clear margin, 5 cases had lobulation sign, 3 cases had spiculation,10 cases had vacuole sign, 3 cases had bronchiolectasis sign, 8 cases hadpleura indentation. 30 lesions from the adjacent pleura distance ≤ 10 mm, accounting for 62.5%. Conclusion: The HRCT of AIS were characterized by pGGN, (-611±82.76) HU, less than 20mm, clear edge; the lobulation, spiculation, and vacuole sign were rare. HRCT helps AIS display and early diagnosis.